1. Field of the Invention
The present application relates to the use of the characteristics of an ion current sensor signal for onboard measurement of in-cylinder variables such as but not limited to soot, engine load, and fuel consumption, and for the control of different engine parameters accordingly.
2. Description of Related Art
One existing technology in quantitative soot measurement utilizes laser techniques in optically accessible engines. These techniques are used in research facilities only and cannot be applied in commercial engines. Another existing technology uses sampling techniques which require very expensive instrumentation and can also only be applied in research labs. Other technologies have provided some results for soot measurement where a sensor is located in the exhaust pipe or within after treatment devices. The problem of this type of sensors is the slow access to the soot measurement data. Furthermore, this type of sensors is unable to predict the amount of soot attributable to each engine cylinder accurately. This brings us to the conclusion that there is no in-cylinder, low cost technology that is capable of quantitatively and adequately predict the amount of soot produced in commercial engines.
As of engine load and fuel flow, there are several methods for which these parameters can be measured, each with their own advantages, disadvantages and applications. One method is to use the engine speed density. The method involves a manifold absolute pressure sensor (MAP) and intake air temperature. Speed density systems are very sensitive to temperature changes which affect load and fuel calculations.